1. Field of the Invention
This invention relates to dispensing assemblies for dispensing individual articles and, more particularly, to cassette dispensing assemblies for dispensing sample support cassette articles for subsequent histological analysis.
2. Description of the Related Art
Biomedical laboratories commonly utilize rectangular plastic trays of a specified size and shape, called sample cassettes, to hold biological samples for histological analysis or other testing. The cassettes are single use disposable articles which are stored in bulk and require individual labeling and dispensing prior to use. The cassettes are generally rectangular and have an angled face for labeling which can be presented to a marking device. One device for marking and dispensing sample cassettes is known as the Shur-Mark Cassette labeler. Another device for labeling and dispensing is illustrated in UK Patent Application GB 2 235 163 A, filed Jun. 28, 1990 in the name of Pauline D. Lamb. Lamb discloses a device for marking supports for laboratory samples, for example (a) laboratory tissue processing cassettes made of plastic material and (b) glass laboratory or microscope slides.
The marking device disclosed in the Lamb patent application comprises a marking stylus operatively coupled to a plotter mechanism for applying a selected marking to the sample support article at a marking locus, with means for holding a sample support article in selected position at the marking locus for the marking operation. This marking device includes a mechanism for ejecting the sample support article from the holding means subsequent to marking of the sample support article.
The sample support articles are supplied to the marking locus of the device disclosed in the Lamb patent application from a magazine mounted above a slide tray extending from an upper feed end downwardly to a lower discharge end communicating with the aforementioned holding means which secure the sample support article during its marking. The magazine is manually loaded, one-by-one, with the sample support articles to form a stack of the articles in the interior volume of the magazine. At the lower portion of the magazine is a rotary reciprocating block of a selected shape which permits the release of a single sample support article at a time, from the magazine, as the block is rotated to its release position and then returned to its "blocking" position, to retain the next succeeding sample support article in the magazine, pending release on the next rotation cycle of the block member.
Although the device of the Lamb patent application is generally reliable and effective for its intended use, it nonetheless suffers from deficiencies which limit its broad applicability.
The magazine in the Lamb device is difficult to manually load in a quick manner, such as may be desired for continuous operation of the device in the service of labeling a large number of support articles. Thus, the sample support articles dropped into the upper end of the magazine housing may, in dropping onto the existing stack of articles, become misregistered in relation to the already stacked articles, with the result that the misregistered article may have to be manually re-registered, or the labeling device may have to be shaken or tapped to cause the misregistered article to properly reseat itself in position on the existing stack of the support articles. Such treatment of the labeling device may in turn cause damage to the device itself and/or cause additional support articles in the previously existing stack to themselves become misregistered. In addition, manual loading of the magazine in the Lamb device is time-consuming, in terms of the associated technician's time, which otherwise could be usefully employed in other laboratory operations.
In addition to the difficulties associated with loading the Lamb device, the reciprocating block mechanism for ejecting the cassettes can function improperly. The block acts as both the release and retention member which can cause misregistration of stacked cassettes.
Accordingly, the Lamb device is difficult to load in a quick fashion while insuring accurate alignment and stacking of the support articles in the vertical feed hopper, and loading in any event is time-consuming and labor intensive. Further, the reciprocating block release mechanism can cause misalignment and consequent improper sample cassette dispensing.
The majority of commercially available cassette articles in use in Europe have a frontal surface for labeling which defines a face angle of 30.degree. with respect to the bottom main surface of the cassette article. A majority of cassette articles in use in the United States have a frontal surface for labeling which defines a face angle of 45.degree. with respect to such bottom surface of the cassette article, while cassette articles with a 30.degree. face angle are also significantly used. In Japan, 40.degree. cassette articles are predominantly employed. The Lamb patent application device readily accommodates the 30.degree. cassette articles, but does not permit the 45.degree. cassette articles or 40.degree. cassette articles to be easily marked in use of the device.